Hello,

Ill start off by saying Im very new to working with embedded systems and do not have much experience at all, so if I ask kind of a dumb question, at least you'll know why

So I am working with the DEMOACKIT from Freescale, with the MCF51AC256.

If I was to hum into a microphone, how could I go about getting the frequency of that hum? I'm pretty sure I'll need to make use of a FIR filter but have never even heard of one before I wanted to do this.

Any help would be greatly appreciated. Again, please excuse my noviceness, I'm learning!

Well I was actually thinking I could use a microphone, amplify it a lot, use a bandpass filter, and when I input it into the processor I would just count the number of zero passes in a given amount of time and that would be my frequency.

Would this work?

Counting the number of zero passes in a given amount of time is non-reliable method of the microphone signal frequency. It demands non-realistic accurate narrow bandpass filtering.

The idea of some preliminary bandpass filtering and the subsequent FFT is seem as the reliable method.

So counting the number of zero passes definitely wouldn't work? Thats a shame, I was hoping it would be that easy...

Now, how exactly would I perform a Fourier Transform on the incoming signal? Is the Fourier transform all software that I would write? Is there some sort of bean that I should download for this to work? Or would the signal just be going into a AD converter and I would analyze it from there?

Again, sorry for the novice questions but this is all new to me and I'm i the process of learning all of this right now.

Arrange some analog conditioning: at least amplification and antialiasing low-pass filter. It will be also good to cut sure the non-interesting frequencies.

Arrange sampling the signal with a reasonable sampling frequency and quantity of samples.

Apply windowing.

Apply FFT.

Analyse the spectra.

Useful resources:

The Freescale source code DSP libraries:

http://www.freescale.com/files/32bit/doc/ref_manual/DSPLIBUM.pdf?fsrch=1

"This document provides a library of macros designed to ensure efficient programming of the ColdFire processor using MAX..."

http://www.freescale.com/webapp/sps/download/license.jsp?colCode=DSPLIBUMSW&location=null&fsrch=1

"Accompanying software to the "Digital Signal Processing Libraries Using the ColdFire eMAC and MAC User's Manual"

https://www.freescale.com/webapp/Download?colCode=CFLMOPMSW&appType=license&location=null&fsrch=1

"Software for the CFLMOPM"

"Telling you what you really need to know about noise & vibration measurement". Includes explanation of many practical issues:

Thanks for the sources yevgenit!

Ill definitely check those out.